See what Mailchimp campaign openers paid in FreshBooks

**Objective:** For campaign `{campaign-id}`, find the openers who are FreshBooks clients and report what they have paid, looking back `{lookback-days}` days (default 90) from today.

**Step 1: Get the openers (mailchimp server)**

Call `mailchimp-get-campaign` with `campaign-id` set to `{campaign-id}` to confirm the campaign and note its `title` and `send-date`. If it is not found, stop. Then call `mailchimp-get-campaign-open` with `campaign-id` and `max-records` 200. Keep `email` and `opens`.

**Step 2: Match to FreshBooks clients (freshbooks server)**

For each opener call `freshbooks-get-client` with `email` set to the opener's email (and `company` `{company}` if given). Keep only matches.

**Step 3: Payments (freshbooks server)**

For each matched client call `freshbooks-get-payment` with `client-id` set to the client's `id` and `date.from` set to the start of the lookback window. Total the amount per client, grouped by currency.

**Step 4: Report**

Campaign title and send date, number of openers, number matched to clients, and a table of matched clients with opens, payments in the window and last payment date. Close with the total paid by openers and the share of openers who are clients.

**Rules & Guidelines:**

* `mailchimp-get-campaign` and `mailchimp-get-campaign-open` are on the mailchimp server. `freshbooks-get-client` and `freshbooks-get-payment` are on the freshbooks server.
* Say plainly that this shows association, not that the campaign caused the payment.
* Read-only. Do not call any add, update or delete tool on either server, and do not call `mailchimp-replicate-campaign`.

**Validation:**

* If nobody opened the campaign, report that and stop.
* If no opener is a FreshBooks client, report that rather than guessing at name matches.